Caption: Brain variation. Coloured composite three- dimensional scan of the variation in the structure of the human ventricles, the fluid-filled cavities of the brain. It was created from magnetic resonance imaging (MRI) scans of various healthy brains. The front of the brain is at right. The amount of variation is shown by colour-coded ovals that range from red (greatest), through yellow and green, to blue. MRI scans are slice images through the body made using a powerful magnet and pulses of radio waves. Successive slices can be combined to produce a three-dimensional image using a computer. This scan was produced at the Laboratory of Neuro Imaging (LONI) at UCLA, USA.